1. Field of the Invention
The present invention relates to disc type valve assemblies. Although not limited thereto, the invention is particularly adapted to damper valves which are used in environments in which a tight leakproof seal between the valve element and valve seat is imperative.
For example, in tankers used to transport oil and other flammable liquids, an inert gas is customarily used to fill the air space above the liquid level of the flammable liquid in order to prevent explosions. A convenient source of such inert gas is the exhaust from the diesel engines of the vessel, and such is conveyed to the storage vessels via suitable conduits. It is periodically necessary to close these conduits to permit maintenance work on filters or other apparatus therein, or on the conduits themselves. Closing of the conduits is customarily accomplished by damper valves in the conduits.
During such maintenance periods, it is imperative that a tight leakproof seal be maintained by the damper valve to prevent leakage of the inert gas and asphyxiation of the workers. However, during such times as the valve is open, solids tend to build up on the valve seat, and these deposits interfere with the effectiveness of the seal between the valve element and the seat.
2. Description of the Prior Art
Several techniques have been attempted in dealing with the aforementioned problem of solid deposits on valve seats. One is the provision of hollow valve elements having jets for the direction of air onto the valve seat to clear the latter. In another system, such jets are provided in the pipes and/or flanges between which the valve is disposed and directed at the valve element. Neither of these techniques has been satisfactory.